Why do biologists focus on the issue of adaptation of species?

Biodiversity is viewed as an important indication of the health of ecosystems. Why do some biomes show little biodiversity but are still regarded as healthy?

Why do some biologists view human beings as the most adaptable and successful species on the planet?

Biologists focus on adaptation of species to determine the rate of its continuity and to learn whether the ecosystems that they are living in are still healthy and can support life.

Though organisms have little biodiversity, the immediate environment with which they live in and the existence of other organisms thriving within that population is still a determining factor to declare it as a healthy environment.

Humans are the most adaptable and successful species on the planet because of the capacity of our brain to evolve and adapt to the changes that we see around us.